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    SubjectRe: [PATCH v5 0/5] iommu: Retire detach_dev callback
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    Hi All,


    On 10.01.2023 03:54, Lu Baolu wrote:
    > Hi folks,
    >
    > The iommu core calls the driver's detach_dev domain op callback only when
    > a device is finished assigning to user space and
    > iommu_group_release_dma_owner() is called to return the device to the
    > kernel, where iommu core wants to set the default domain to the device but
    > the driver didn't provide one. The code looks like:
    >
    > /*
    > * New drivers should support default domains and so the detach_dev() op
    > * will never be called. Otherwise the NULL domain represents some
    > * platform specific behavior.
    > */
    > if (!new_domain) {
    > if (WARN_ON(!group->domain->ops->detach_dev))
    > return -EINVAL;
    > __iommu_group_for_each_dev(group, group->domain,
    > iommu_group_do_detach_device);
    > group->domain = NULL;
    > return 0;
    > }
    >
    > In other words, if the iommu driver provides default domains, the
    > .detach_dev callback will never be called; Otherwise, the .detach_dev
    > callback is actually called to return control back to the platform DMA
    > ops, other than detaching the domain from device.
    >
    > This series cleanups this by:
    >
    > - If the IOMMU driver provides default domains, remove .detach_dev
    > callback.
    > - Adds a new set_platform_dma iommu op. Any IOMMU driver that doesn't
    > provide default domain should implement set_platform_dma callback
    > instead.
    > - Retire .detach_dev callback.
    >
    > This series originates from various discussion in the community. Thanks
    > to Jason, Robin and all others for their ideas.

    I wonder how to handle the ARM 32bit case, which doesn't use the default
    domain solution. Today, once this patchset has been merged to
    linux-next, I've noticed that it broke booting of ARM 32bit Exynos based
    boards.

    The final solution would be to switch ARM 32bit to generic DMA-IOMMU
    glue, but I'm not sure it this will happen soon. I will try to check if
    any kind of quick workaround can be applied to get it working again.


    > The whole series is available on github:
    > https://protect2.fireeye.com/v1/url?k=ef2183b6-b0bababa-ef2008f9-000babff3563-336828b3433153d2&q=1&e=4ae5dae4-383f-4a82-9449-3f08f0422cb1&u=https%3A%2F%2Fgithub.com%2FLuBaolu%2Fintel-iommu%2Fcommits%2Fiommu-retire-detach_dev-v5
    >
    > Change log:
    > v5:
    > - Merge some patches to make the series cute. No functionality changes.
    > - Check the op directly and WARN_ON the lack of any necessary
    > callbacks. Get rid of the ret and EINVAL.
    >
    > v4:
    > - https://lore.kernel.org/linux-iommu/20230104125725.271850-1-baolu.lu@linux.intel.com/
    > - Drop the patch which renamed .attach_dev to .set_dev. As Robin said,
    > "... I also wouldn't say that "attach" loses its meaning in a context
    > where an equivalent "detach" operation is only ever implicit in
    > reattaching to something else...". If we have a better name in the
    > future, we can do it in other series.
    > - Adjust the patch of "iommu: Add set_platform_dma_ops iommu ops"
    > according to Jason's following suggestion " ... This is a bit ugly,
    > it would be better to make the previous patch call set_platform_dma
    > if it is set instead of detach_dev and then these patches should just
    > rename the driver's fsl_pamu_detach_device to
    > fsl_pamu_set_platform_dma ..."
    > - Add a new patch to remove deferred attach check from
    > __iommu_detach_domain() path. Make it a separate patch as the
    > prerequisite to remove __iommu_detach_device() helper.
    > - Rename set_platform_dma to set_platform_dma_ops to make it more
    > meaningful.
    >
    > v3:
    > - https://lore.kernel.org/linux-iommu/20221128064648.1934720-1-baolu.lu@linux.intel.com/
    > - Setting blocking domain is not conceptually equal to detach_dev.
    > Dropped all blocking domain related staffs in the previous version.
    >
    > v2:
    > - https://lore.kernel.org/linux-iommu/20220826123014.52709-1-baolu.lu@linux.intel.com/
    > - Replace .detach_dev callback with static block domain ops;
    > - Rename .attach_dev to .set_dev.
    >
    > v1:
    > - https://lore.kernel.org/linux-iommu/20220516015759.2952771-1-baolu.lu@linux.intel.com/
    >
    > Jason Gunthorpe (1):
    > iommu: Remove deferred attach check from __iommu_detach_device()
    >
    > Lu Baolu (4):
    > iommu: Remove detach_dev callbacks
    > iommu: Add set_platform_dma_ops iommu ops
    > iommu: Add set_platform_dma_ops callbacks
    > iommu: Remove detach_dev callback
    >
    > include/linux/iommu.h | 8 ++-
    > include/trace/events/iommu.h | 7 --
    > drivers/iommu/amd/iommu.c | 26 -------
    > drivers/iommu/apple-dart.c | 24 -------
    > drivers/iommu/arm/arm-smmu/qcom_iommu.c | 23 ------
    > drivers/iommu/exynos-iommu.c | 1 -
    > drivers/iommu/fsl_pamu_domain.c | 6 +-
    > drivers/iommu/iommu-traces.c | 1 -
    > drivers/iommu/iommu.c | 94 ++++++++++++-------------
    > drivers/iommu/ipmmu-vmsa.c | 16 -----
    > drivers/iommu/msm_iommu.c | 6 +-
    > drivers/iommu/mtk_iommu.c | 9 ---
    > drivers/iommu/mtk_iommu_v1.c | 4 +-
    > drivers/iommu/omap-iommu.c | 6 +-
    > drivers/iommu/rockchip-iommu.c | 1 -
    > drivers/iommu/s390-iommu.c | 7 +-
    > drivers/iommu/sprd-iommu.c | 16 -----
    > drivers/iommu/sun50i-iommu.c | 1 -
    > drivers/iommu/tegra-gart.c | 6 +-
    > drivers/iommu/tegra-smmu.c | 5 +-
    > 20 files changed, 69 insertions(+), 198 deletions(-)
    >
    Best regards
    --
    Marek Szyprowski, PhD
    Samsung R&D Institute Poland

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